Process for continuous polymerization of olefin monomers in a reactor

ABSTRACT

The invention relates to a process for the continuous polymerization of one or more a-olefin monomers of which at least one is ethylene or propylene comprising the steps of: (1) feeding the one or more a-olefins to a vertically extended reactor suitable for the continuous fluidized bed polymerization of one or more a-olefin monomers of which at least one is ethylene or propylene, which reactor is operable in condensed mode, wherein the reactor comprises a distribution plate and an integral gas/liquid separator located below the distribution plate, (2) withdrawing the polyolefin from the reactor (3) withdrawing fluids from the top of the reactor, (4) cooling the fluids to below their dew point, resulting in a bottom recycle stream, (5) introducing the bottom recycle stream under the distribution plate, (6) separating at least part of the liquid from the bottom recycle stream using the integral separator to form a liquid phase and a gas/liquid phase, (7) feeding the liquid phase to an external pipe, (8) adding a solid polymerization catalyst to the liquid phase in the external pipe resulting in the formation of a slurry stream comprising prepolymer and/or polymer and (9) feeding the slurry stream comprising the prepolymer and/or polymer into the reactor above the distribution plate, wherein the prepolymer and/or polymer are present in the slurry stream in an amount of from 0.01 to 99 wt % based on the total slurry stream upon introduction of the slurry stream into the reactor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No.PCT/EP2014/075411, filed Nov. 24, 2014, which claims priority to U.S.Application No. 61/929,599, filed Jan. 21, 2014, and EuropeanApplication No. 13195140.2, filed Nov. 29, 2013, all of which areincorporated herein by reference in their entirety.

The invention relates to a process for the continuous polymerization ofolefin monomers in a reactor, to a reaction system suitable for use insaid process and to polyolefins obtainable with said process.

There are many different processes for the polymerization of olefinmonomers, including gas-phase fluidized bed processes, slurry, loop orstirred tank reactors, suspension and solution processes.

The discovery of the process for the production of polyolefins influidized beds has provided a means for the production of a diversearray of polyolefins such as polyethylene, polypropylene, and polyolefincopolymers. Using a fluidized bed polymerization process substantiallyreduces the energy requirements as compared to other processes and mostimportantly reduces the capital investment required to run such aprocess to produce polymers.

Gas fluidized bed polymerization plants generally employ a continuouscycle. In one part of the cycle, in a reactor a cycling gas stream isheated by the heat of polymerization. This heat is removed in anotherpart of the cycle by a cooling system external to the reactor.

However, gas fluidized bed reactors include various limitations, forexample they have a limited heat removal of the heat produced during theexothermic polymerization of the olefin monomers. If heat is notsufficiently removed, various undesired effects occur, such asdegradation of the polymerization catalyst, degradation of polyolefinproduced, agglomeration of the polyolefin and/or chunking of thepolyolefin. Consequently, the overall effect of a limitation in heatremoval, is a limitation of the rate of production of the polyolefin.

Consequently, there have been many developments to increase heatremoval.

For example, a more efficient way to achieve heat removal is byoptionally introducing an inert condensing agent and cooling the gaseousrecycle stream to a temperature below its dew point, resulting in thecondensation of at least part of the recycle stream to form a bottomrecycle stream containing liquid and gas. The thus formed bottom recyclestream is then introduced into the fluidized bed polymerization reactor,where the liquid portion will vaporize upon exposure to the heat of thereactor, which vaporization will remove heat from the reactor. This modeof operation is known in the art as a “condensing mode” or “condensedmode” process.

However, the heat removal that can be achieved in such condensed mode isstill limited, since the current reactors, reaction systems andprocesses for the production of polyolefins using a fluidized bed and acondensed mode do not allow large amounts of liquid in the recyclestream as this causes destabilization of the fluidized bed.

For example, EP 89 691 A2 discloses a process for increasing polymerproduction in a fluidized bed reactor employing an exothermicpolymerization reaction by cooling the recycle stream to below its dewpoint and returning the resultant two-phase fluid stream to the reactorto maintain the fluidized bed at a desired temperature above the dewpoint of the recycle stream. The inventors of EP 89 691 A2 found thatthe amount of condensation of liquid in the recycle stream could bemaintained at up to about 20 percent by weight.

For example, WO00/44792A1 discloses a continuous process for themanufacture of olefin polymers in a continuous gas phase polymerizationreaction wherein monomer, after passage through the fluidized bed, iscooled to a temperature below its dew point to produce a mixture of coldgas and liquid. All or part of the cold gas is introduced into thebottom of the reactor to serve as the fluidizing gas stream for thefluidized bed. Cold liquid separated from the liquid is warmed to form aheated fluid by passing in indirect heat exchange relation with thefluidized bed and the heated fluid is then injected directly into thebed; combined with the fluidizing gas stream; sprayed on top of the bedor combined with gaseous monomer removed from the fluidized bed forcooling.

In order to increase the cooling capacity and therefore the productionrate, it is therefore desirable to allow larger amounts of liquid in therecycle stream without causing destabilization of the fluidized bed.

Therefore, it is the object of the invention to provide a process forthe continuous polymerization of olefin monomers in a fluidized bedreactor, wherein larger amounts of liquid can be maintained in therecycle stream.

This object is achieved by a process for the continuous polymerizationof one or more α-olefin monomers of which at least one is ethylene orpropylene comprising the steps of:

(1) feeding the one or more α-olefins to a vertically extended reactorsuitable for the continuous fluidized bed polymerization of one or moreα-olefin monomers of which at least one is ethylene or propylene, whichreactor is operable in condensed mode, wherein the reactor comprises adistribution plate and an integral gas/liquid separator located belowthe distribution plate(2) withdrawing the polyolefin from the reactor(3) withdrawing fluids from the top of the reactor(4) cooling the fluids to below their dew point, resulting in a bottomrecycle stream(5) introducing the bottom recycle stream under the distribution plate(6) separating at least part of the liquid from the bottom recyclestream using the integral separator to form a liquid phase and agas/liquid phase(7) feeding the liquid phase to an external pipe(8) adding a solid polymerization catalyst to the liquid phase in theexternal pipe resulting in the formation of a slurry stream comprisingprepolymer and/or polymer and(9) feeding the slurry stream comprising the prepolymer and/or polymerinto the reactor above the distribution plate, wherein the prepolymerand/or polymer are present in the slurry stream in an amount of from0.01 to 99 wt %, for example to 90 wt %, for example to 70 wt %, forexample to 60 wt % based on the total slurry stream upon introduction ofthe slurry stream into the reactor.

In this context, liquid phase means liquid, whereas gas/liquid phasemeans a stream comprising gas and liquid.

It has been found that by the process of the invention, it is possibleto introduce larger amounts of liquids, for example up to 50 wt %liquids based on total feed into the reactor without destabilization ordefluidization of the fluidized bed. Further, by using the process ofthe invention, the superficial gas velocity in the reactor may beincreased.

Furthermore, with the process of the invention, an increase in thespace-time-yield of a reactor may be obtained. In other words, the rateof the production of the polyolefin within a multi-zone reactor of thesame size may be increased, for instance by 20%, using the process ofthe invention.

Also, with the process of the invention, the catalyst productivity maybe improved, for example by 10%.

Moreover, in the process of the invention less fines and less staticsmay be produced, which may lead as a consequence to a) a reduction infouling of the distribution plate and/or b) less sheeting on the reactorwall.

Also, it is possible to perform the (pre)polymerization at conditionsdifferent from the conditions in the multi-zone reactor, making itpossible to produce a wide variety of different polyolefins.

The polyolefins that may be produced in the process of the invention mayhave a higher bulk density and/or a higher homogeneity.

The one or more α-olefin monomers may be fed to the reactor, preferablya multi-zone reactor using feeding means such as a pump. The monomersare preferably fed to the reactor by adding the monomers to the fluidsthat are circulated from the top of the reactor to the first zone priorto cooling of the fluids. Preferably, the one or more α-olefin monomersare added in such amounts that they make up for the one or more α-olefinmonomer consumed during the polymerization.

The one or more α-olefin monomers may be fed in one or in multiplefeeding streams. For example, one type of olefin monomer, typicallyethylene and/or propylene may be comprised in the feed (60) and anothertype of α-olefin monomer, also referred to herein as the comonomer, maybe comprised in the feed (70).

Withdrawal of the polyolefin (30) from the reactor may be done at anyposition in the area above the distribution plate or at a combination ofpositions, for example in case of the multi-zone reactor as describedherein, the polyolefin may be withdrawn from the bottom part of thesecond zone (2), the top part of the second zone (2), the bottom part ofthe third zone (3) and/or the top part of the third zone (3).Preferably, in case of the multi-zone reactor the polyolefin iswithdrawn from the bottom part of the second zone (2) and/or from thebottom part of the third zone (3).

Polyolefin (30) may be withdrawn from the reactor using any suitablemeans, for example a polymer discharge system. The polyolefin may beused as such or may be subjected to purification or otherend-processing.

The fluids may be withdrawn from the top of the reactor using anysuitable means, for example a compressor may be used.

With ‘continuous polymerization of one or more α-olefins’ or ‘continuouspreparation of polyolefin’ is meant herein that one or more α-olefinmonomers of which at least one is ethylene or propylene are fed to themulti-zone reactor and polyolefin thus produced is (semi)-continuouslywithdrawn through a polymer discharge system connected to the multi-zonereactor.

In the process for the continuous polymerization one of the α-olefinmonomers is ethylene or propylene. Other α-olefin monomers may bepresent. Examples of other α-olefin monomers include for exampleα-olefins having from 4 to 8 carbon atoms. However, small quantities ofα-olefin monomers having more than 8 carbon atoms, for example 9 to 18carbon atoms, such as for example a conjugated diene, can be employed ifdesired. Thus it is possible to produce homopolymers of ethylene orpropylene or copolymers of ethylene and/or propylene with one of moreα-olefin monomers having from 4 to 8 α-olefin monomers. Preferredα-olefin monomers include but are not limited to but-1-ene, isobutene,pent-1-ene, hex-1-ene, hexadiene, isoprene, styrene, 4-methylpent-1-ene,oct-1-ene and butadiene. Examples of α-olefin monomers having more than8 carbon atoms that can be copolymerized with an ethylene and/orpropylene monomer, or that can be used as partial replacement forα-olefin monomers having from 4 to 8 α-olefin monomers include but arenot limited to dec-1-ene and ethylidene norbornene.

When the system or process of the invention is used for thecopolymerization of ethylene and/or propylene with α-olefin monomers,the ethylene and/or propylene preferably is used as the major componentof the copolymer. For example, the amount of ethylene and/or propylenepresent in the copolymer is at least 65% by weight, for example at least70% by weight, for example at least 80% by weight based on the totalcopolymer.

With ‘condensed mode’ is meant that a liquid containing stream is usedto cool the reactor (8).

The distribution plate (6) may be any device that is suitable fordistributing the bottom recycle stream in the multi-zone reactor (8) tokeep a fluidized bed in the second zone (2) of the multi-zone reactor(8) and to serve as a support for a quiescent bed of the solidpolymerization catalyst and polyolefin when the multi-zone reactor (8)is not in operation. For example, the distribution plate may be ascreen, slotted plate, perforated plate, a plate of the bubble-cap type,or other conventional or commercially available plate or other fluiddistribution device. An example of a commonly used type of distributionplate is a perforated plate with some above-hole structure on top ofeach hole, to prevent particle sifting. In the figures, the distributionplate (6) is indicated with a dotted line.

The distribution plate is generally positioned perpendicular to thelongitudinal axis of a reactor, wherein the fluidized bed is locatedabove said distribution plate and a mixing chamber region (zone 1) belowsaid distribution plate.

The distribution plate is used for achieving good gas distribution. Itmay be a screen, slotted plate, perforated plate, a plate of thebubble-cap type, or the like. The elements of the plate may all bestationary or the plate may be of the mobile type disclosed in U.S. Pat.No. 3,298,792. Mechanically swept distribution grids are described inU.S. Pat. No. 3,254,070. Whatever its design, it must diffuse therecycle fluid through the particles at the base of the bed to keep thebed in a fluidized condition and also serve to support a quiescent bedof resin particles when the reactor is not in operation.

For purpose of this invention, the preferred type distribution plate isgenerally of the type which is fabricated from metal and which has holesdistributed across its surface. The holes are normally of a diameter ofabout one-half inch. The holes extend through the plate and over theholes there are positioned angle caps which are fixedly mounted to theplate. Alternate rows of angle irons are oriented at angles to eachother, preferably at 60 degrees, in alternate parallel alignment asshown in FIG. 4 of U.S. Pat. No. 4,933,149. They serve to distribute theflow of fluid along the surface of the plate so as to avoid stagnantzones of solids. In addition, they prevent resin particles from fallingthrough the holes when the bed is settled or quiescent.

The distribution plate may for example have the shape of a cone, as forexample described in U.S. Pat. No. 2,602,647A1, hereby incorporated byreference, which describes a conical distribution plate having a portedcentral conical section and a ported outer annular conical section, theports in said central conical section and said annular conical sectionbeing circumferentially offset so as to provide a substantial deflectingsurface on said central section extending to the ports in the annularsection.

Other conical shapes of the distribution plate are for example describedin U.S. Pat. No. 4,518,750, hereby incorporated by reference, whichdescribes a distributor of fluidization gases which comprises a doublecone body consisting of: (a) a lower conical element, arranged with thevertex turned downwards, provided with more than two ribs on the lateralsurface, said ribs having such a profile as to form, together with thewall of the containing shell, flow channels with a decreasingcross-section in an upward direction so that the velocity of the gaswill increase gradually and correspondingly, the ribs being arrangeddiametrically opposite to each other with an axial symmetry and with aninclination with respect to the vertical such as to impart to theinflowing gas current a tangential component, the profile andinclination of the ribs being such as to allow the passage of the solidparticles entrained by the inflowing gas, and so as to hinder thefalling back of the particles of the fluidized bed whenever the feedingin of the gas is interrupted; and of (b) an upper conical element, withits vertex turned upwards, superimposed onto the lower conical elementand having the function of activating the circulation of the solid inthe fluidized bed, eliminating the dead or stagnation zones, saidprocess being further characterized in that the distributor in the fluidbed reactor in which it is carried out comprises devices for recyclingof the gas, which distributor and the recycling devices allow thepassage of the solid particles of the fluidized material entrained bythe recycling gas.

For example, U.S. Pat. No. 5,143,705, hereby incorporated by reference,describes a conical distribution plate with its apex pointing upwardly,wherein said conical distribution plate has a plurality of openings.

For example, U.S. Pat. No. 7,226,565B2, hereby incorporated byreference, discloses a distribution plate having a plurality of gas floworifices whose outlet sides are sidened conically, said outlet sidesbeing wider than the inlet sides.

For example U.S. Pat. No. 5,627,243, hereby incorporated by reference,discloses a cap-like low control elements formed by a cone with asurface of revolution having its tip pointed upward. The conical surfaceof the flow control element is provided with preformation which isarranged substantially evenly divided on all side surfaces of theelement.

For example, U.S. Pat. No. 5,381,827 discloses a gas distributor for usein a gas phase polymerization apparatus having an agitator in afluidized bed polymerization reactor, the gas distributor beingcharacterized in that the distributor has holes each covered with a capfrom above, the cap having an opening oriented in a substantiallyhorizontal direction at an angle of about 90 to 135° with, and outwardlyof, a tangent to a circle centered about the center of the reactor.

Preferably, in the invention, the distribution plate comprises a conicalshape.

In addition to the distribution plate, the reactor may be furtherequipped with other means for agitation, such as mechanical agitation,for example a stirrer. Preferably, the reactor does not comprisemechanical agitation.

For the avoidance of doubt the term ‘fluids’ encompasses liquids, gasesand mixtures thereof, wherein the term ‘liquids’ includes liquidscontaining solid particles, such as slurries.

The fluids may be cooled to below the dew point of the fluids using anysuitable cooling means. For example, cooling of the fluids may beperformed using a cooling unit. The dew point may be increased byincreasing the operating pressure of the fluids and/or by increasing thepercentage of condensable fluids and simultaneously decreasing thepercentage of non-condensable gases in the fluids.

Introduction of the bottom recycle stream under the distribution platemay be done using any suitable means for introducing fluids, for exampleusing injection nozzles.

By separating the liquid stream from the bottom recycle stream, aremaining gas/liquid stream will be passed from below the distributionplate (the first zone (1) in case of the multi-zone reactor) through thedistribution plate (6) into the zone above the distribution plate (thesecond zone (2) in case of the multi-zone reactor). The separated liquidstream to which the solid catalyst (20) is fed will become a slurrystream comprising a prepolymer and/or polymer, which is fed to the areaabove the distribution plate, preferably into the fluidized bed, wherethe prepolymer and/or polymer will be converted into the polyolefin inthe upper part of the reactor (the second and/or the third zone in caseof the multi-zone reactor). Heat generated by the polymerization willcause the liquids in the fluids to evaporate. Polyolefin (30) iswithdrawn from the (multi-zone) reactor (8). Unreacted fluids arerecirculated from the top of the multi-zone reactor (8) to the firstzone (1). The one or more olefin monomers and other fluids, such ashydrogen, an inert gas or liquid, for example a condensable non-reactivemonomer, may be added to the unreacted fluids to make up for reactedfluids before cooling the fluids to below the dew point of the fluids toform a bottom recycle stream.

With integral separator is meant a separator that is located inside themulti-zone reactor. The integral separator is located under thedistribution plate.

An example of an integral separator includes a hydrocyclone, a cyclone,wet scrubber and a centrifuge, any of which may optionally be combinedwith a flow deflector and/or a spinner. In such separator, due to thecentrifugal effect, the bottom recycle stream is forced to furthercondense, thereby increasing the liquid weight fraction.

Preferably, a hydrocyclone is used. Hydrocyclones are commerciallyavailable.

The integral separator may achieve separation by using one or morebaffles, for example which baffles are placed near the point ofintroduction of the bottom recycle stream into the multi-zone reactor.The presence of said baffle or baffles causes (at least part of the)condensed liquid in the bottom recycle stream to coalescent in the formof liquid droplets on the baffles, which droplets will then subsequentlyfall to the bottom part of the reactor (8) by gravity.

Therefore, in one embodiment of the invention, the integral separator(9) comprises one or more baffles.

The integral separator may have a volume of between 20 and 80 m³.Preferably, the diameter of the integral separator is the same as thediameter of the distribution plate, for example, a diameter of up to 5m, for example a diameter in the range from 2 to 4, for example in therange from 2 to 3 m.

Preferably, the integral separator comprises a demister. Demisters arewell known in the art.

Preferably, the integral separator further comprises a liquid reservoirin the bottom of the integral separator for collection of the liquidphase (the bottom of the integral separator is (located in) the bottomof the reactor). The liquid reservoir enables the liquid to be collectedthereby providing control over the discharge of the liquid from theintegral separator.

Usually, the residence time in the integral separator is low, forexample, in the range of 0.1 second to 5 minutes, for example from 1second to 1 minute.

Preferably, the integral separator is a hydrocyclone, cyclone or a wetscrubber, each of which may optionally be combined with a flow deflectorand/or spinner, preferably the integral separator is a hydrocyclone.

The liquid phase is fed to an external pipe, preferably using a pump,preferably a slurry pump. This external pipe preferably has a diameterof from 2 to 20% of the largest diameter of the multi-zone reactor.

In a special embodiment, the external pipe may comprise a loop reactor.A loop reactor as defined herein is a pipe having a diameter of forexample at least 10 cm, for example at least 25 cm and a length of forexample at least 15 m, for example a length of around 75 m, which isarranged in the form of a loop. In case of the present invention, whenthe external pipe comprises a loop reactor, the external pipe may bedivided into two pipes that are each independently connected the inletand the outlet of the loop reactor. The loop reactor may be equippedwith a cooling jacket, for example a cooling jacket using water ascoolant. The liquid phase/liquid stream comprising (pre)polymer may bepumped around in the loop reactor at a high velocity, for example avelocity of from 6 to 10 m/s, for example using an inline axial pump.The loop reactor preferably has a high surface to volume ratio, whichfacilitates heat transfer and permits short residence times. The loopreactor may comprise any number of pipes, for example two, four or sixpipes (multi-leg loop reactor), which pipes may be placed in thevertical direction or in the horizontal direction. Preferably, there isno separation between the pipes. The rate of circulation in the loopreactor may for example be in the range from 30 to 2500 times/h.Preferably, the pipes of the loop reactor are placed in the verticaldirection. In the process of the invention, the catalyst may be fed intothe loop reactor.

The external pipe may for example have a length of at least 10 m and forexample a diameter in the range of from 2 to 20%, for example from 5 to15%, for example from 5 to 10% relative to the largest diameter of themulti-zone reactor (8). For example, the largest diameter of themulti-zone reactor (8) may be in the range from 4 to 12 m and thediameter of the external pipe may for example be in the range from 10 to80 cm.

The solid polymerization catalyst may be fed to the external pipe forexample by using feeding means, for example using a pump or anotherinjection means. The solid polymerization catalyst may be injected intothe external pipe as a dry catalyst, but is preferably injected as a wetsolid polymerization catalyst (that means a catalyst in a slurry form).

This is illustrated in FIGS. 1-7 as catalyst feed (20′).

The solid polymerization catalyst may for example be fed as a suspensionin a solvent, for example a hydrocarbon solvent or the like, or in aninert gas, such as nitrogen or may be fed in the form of a prepolymer.

With prepolymer as used herein is meant a polymer wherein the weightratio of polymer to solid polymerization particle onto which it isattached is below 3000 g polymer/g solid polymerization catalyst.

In the processes and reaction system of the invention, in the externalpipe, polymers will be formed on the solid polymerization catalystparticles.

Generally, the prepolymer formed in the processes and reaction system ofthe invention will contain less than 1500 g polymer/g solidpolymerization particle, for example less than 150 g polymer/g solidpolymerization particle, preferably the prepolymer formed in theprocesses and reaction system of the invention will contain from 5 to250 g polymer/g solid polymerization particle.

In addition to feeding the solid polymerization catalyst to the externalpipe, the catalyst may additionally be fed to the reactor at anotherposition. For example, the catalyst may be included in another feed tothe reactor, for example in the feed (60) or in the feed (70) or it maybe fed to the reactor directly. For example, the solid polymerizationcatalyst may be fed at any position into the reactor, for example in thearea above the distribution plate or at a combination of positions, butpreferably, in case of the multi-zone reactor, it is fed to the secondzone (2), preferably to the bottom part of the second zone (2)(indicated in the figures as 2A).

For instance, in case of the multi-zone reactor as described herein, thesolid polymerization catalyst may also be injected into the second zone(2) as a dry catalyst.

The person skilled in the art is aware of which solid polymerizationcatalysts are suitable for continuous polymerization of α-olefinmonomers.

For example, heterogeneous polymerization catalysts, which are catalyststhat are supported on an inert substrate, for example silica or aluminamay be used. Suitable examples of hetereogeneous catalysts includesupported Ziegler Natta and supported metallocene catalysts andcombinations thereof, for example in a mixed catalyst system. Examplesof a catalyst composition for polymerization of α-olefins comprising atleast two catalytic components are for example described in EP1764378A1,hereby incorporated by reference. EP1764378A1 discloses a catalystcomposition comprising a metallocene component and a Ziegler-Natta typetransition metal component, at least one activator and support material.Metallocene catalysts are for example described by Hamielec and Soaresin “Polymerisation reaction engineering-metallocene catalysts” (Prog.Pol. Sci. Vol. 21, 651-706, 1996), hereby incorporated by reference. Thesolid polymerization catalyst may also be a metal oxide catalyst, forexample a chromium oxide catalysts. Such metal oxide catalyst may forexample be based on a support of an inert substrate, for example onsilica, alumina silicate or alumina, for example on a highly poroussupport of silica, alumina silicate or alumina as for example disclosedin the “Handbook of Polyethylene” by Andrew Peacock at pages 61-62,hereby incorporated by reference.

The group of metallocene catalysts includes many variations. In the mostgeneral form, metallocene catalysts comprise a metal atom, for exampletitanium, zirconium or hafnium attached to for example four ligands, forexample two substituted cyclopentadienyl ligands and two alkyl, halideor other ligands with an optionally modified organoalumoxane asactivator, for example methylaluminoxane (MAO) or a compound based onboron. Examples of inert substrates that can be used as support for ametallocene catalyst include inorganic oxides, for example SiO₂, MgCl₂,Al₂O₃, MgF₂ and CaF₂. Preferably, the solid polymerization catalyst usedin the system and process of the invention is a metallocene catalystsupported on silica, for example a silica as commercially available, forexample Grace Davison 948 silica or Ineos ES 70 silica.

A Ziegler Natta catalyst may be used together with a cocatalyst in thesystem and process of the invention. Suitable example of cocatalystsinclude but are not limited to organo aluminium compounds having formulaAIR3, wherein R stands for a hydrocarbon having 1 to 10 C-atoms.Examples of organo aluminium compounds having formula AIR3 includetriethylaluminium alkyl, triisobutyl aluminium trialkyl, tri-n-hexylaluminium and tri octyl aluminium.

Examples of inert substrates that can be used as support for a ZieglerNatta catalyst include inorganic oxides, for example oxides of silica,alumina, magnesium, titanium and/or zirconium; magnesium chloride,clays, zeolites, polystyrene, polyethylene, polypropylene, graphiteand/or layered silicates.

It will be clear to the person skilled in the art, that also mixtures ofsolid polymerization catalysts may be used in the invention. It willalso be clear to the person skilled in the art, that also prepolymer maybe used as solid polymerization catalyst.

Upon introduction of the slurry stream into the reactor, the prepolymerand/or polymer may be present in the liquid stream in an amount of forexample at least 0.01, for example at least 0.05, for example at least0.1, for example at least 1 and/or for example at most 99, for exampleat most 90, for example at most 70, for example at most 60, for exampleat most 50, for example at most 40, for example at most 30, for exampleat most 25% by weight based on the total slurry stream upon introductionof the slurry stream into the reactor.

Preferably, the amount of prepolymer and/or polymer present in theliquid stream is from 1 to 30% by weight based on the total slurrystream upon introduction of the slurry stream into the reactor.

The slurry stream comprising the prepolymer and/or polymer is fed intothe reactor above the distribution plate, preferably directly into thefluidized bed. The slurry stream may be fed at any position into thefluidized bed, but is preferably fed into the lower part of thefluidized bed.

In a preferred embodiment, the reactor is a multi-zone reactor suitablefor the continuous fluidized bed polymerization of one or more α-olefinmonomers of which at least one is ethylene or propylene, whichmulti-zone reactor is operable in condensed mode, which multi-zonereactor comprises a first zone, a second zone, a third zone, a fourthzone and a distribution plate,

wherein the first zone is separated from the second zone by thedistribution plate, wherein the multi-zone reactor is extended in thevertical direction

wherein the second zone of the multi-zone reactor is located above thefirst zone and wherein the third zone of the multi-zone reactor islocated above the second zone, and wherein the fourth zone of themulti-zone reactor is located above the third zone

wherein the second zone contains an inner wall, wherein at least part ofthe inner wall of the second zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactorwherein the third zone contains an inner wall, wherein at least part ofthe inner wall of the third zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactorwherein the largest diameter of the inner wall of the third zone islarger than the largest diameter of the inner wall of the second zone.

In some embodiments, the reactor of the invention may thereby preferablycomprise at least a part of said second zone and/or said third zonecontains an inner wall, wherein at least part of the inner wall has acylindrical shape. The inner wall of the reactor may be the innerenvelope delimiting the reactor.

In the context of the present invention, a gradually increasing diametermay for example mean an increase of the diameter of the inner wall ofthe reactor in the vertical direction towards the top of the reactor.Said increase may be for example stepwise, constant, logarithmic orexponential. One example of such is a continuously opening cone

In the context of the present invention, a continuously opening cone mayfor example mean a conically shaped part of the inner wall of thereactor comprising a first circular opening and a second circularopening connected via the inner wall of the reactor, in which thederivative of the diameter variation of the wall as measured in thevertical direction towards the top of the reactor may preferably have aconstant and positive value.

In some embodiments of the invention, the zone, preferably for examplethe second zone, in the area directly above the distribution plate iseither in the form of a gradually increasing inner diameter or acontinuously opening cone. In the context hereof, directly above maymean for example that a zone in the form of a gradually increasing innerdiameter or a continuously opening cone, wherein the diameter or theopening increases in the vertical direction towards the top of themulti-zone reactor is located relative to the distribution plate, sothat accumulation of liquids on the surface of the distribution platemay preferably be prevented.

A special advantage of the invention may be that it is possible toproduce the polyolefin in the same multi-zone reactor, withoutintermediate separation of the products obtained in the different zones.This as opposed to the reaction systems known so far that containmultiple unit operations and require separation steps in between theunits. Therefore, the invention provides the possibility of shortercycle times for the production of the polyolefin and is easier tooperate.

With ‘multi-zone reactor suitable for the continuous polymerization ofone or more α-olefin monomers of which at least one is ethylene orpropylene’ is meant a device capable of containing and controlling thepolymerization of the one of more α-olefin monomers and which device cancomprise a fluidized bed. The multi-zone reactor of the invention ispreferably closed off at the top and the bottom by a hemisphere.

With ‘fluidized bed’ as used herein is meant that an amount of solidparticles (in this case preferably the solid catalyst and/or the solidcatalyst to which one or more α-olefin monomers of which at least one isethylene or propylene is attached) in a solid/fluid mixture acts as afluid. This can be achieved by placing the amount of solid particlesunder appropriate conditions, for instance by the introduction of fluidthrough the solid particles at a high enough velocity to suspend thesolid particles and causing them to behave as a fluid.

The first zone of the multi-zone reactor is separated from the secondzone by a distribution plate, and is located below the second zone ofthe multi-zone reactor.

In the first zone, a separation and distribution of the gas and liquidmay take place, which is the primary function of the first zone. Thefirst zone may further comprise a flow deflector associated with theentry conduit for providing the bottom recycle stream to prevent theaccumulation of solids and liquids in the first zone. Such flowdeflector is for example described in (the figures of) U.S. Pat. No.4,933,149, hereby incorporated by reference.

The second zone contains an inner wall, wherein at least part of theinner wall of the second zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactor. This leads to a variation of thesuperficial gas velocity at least in a part of the second zone, sincesuperficial gas velocity depends on the circular cross-sectional surfaceinside the reactor. This allows to reduce superficial gas velocity inthe vertical direction towards the top of the multi-zone reactor, sothat the average residence time of polymer particles in the second zonecan be increased as a result.

The continuously opening cone or gradually increasing inner diameter ofthe second zone is preferably located in the lower part of the secondzone, more preferably is located directly above the distribution plate.

The second zone may comprise (part of) the fluidized bed where gas phaseor gas-liquid polymerization may take place. The second zone is suitablefor gas-liquid polymerization (under turbulent fluidization conditions).Turbulent fluidization conditions are described in U.S. Pat. No.6,391,985, hereby incorporated by reference.

In one embodiment of the invention, a gas-liquid polymerization isconducted in the second zone and a gas phase polymerization is conductedin the third zone.

The third zone of the multi-zone reactor is located above the secondzone of the multi-zone reactor. The third zone contains an inner wall,wherein at least part of the inner wall of the third zone is either inthe form of a gradually increasing inner diameter of a continuouslyopening cone, wherein the diameter or the opening increases in thevertical direction towards the top of the multi-zone reactor. This leadsto a variation of the superficial gas velocity at least in a part of thethird zone, since superficial gas velocity depends on the circularcross-sectional surface inside the reactor. This allows to reducesuperficial gas velocity in the vertical direction towards the top ofthe multi-zone reactor, so that the average residence time of polymerparticles in the second zone can be increased as a result.

By using the multi-zone reactor of the invention, in the second zone (2)a gas-liquid polymerization may take place and in the third zone, agas-phase polymerization may then occur. Therefore, the invention mayprovide a two-stage polymerization.

The top zone or fourth zone is a disengagement zone (gas expansionzone), designed so that the superficial gas velocity in that zonepreferably hinders polymer particles to reach and/or stay in that zone.It has the function to disengage the reaction mixture and the polymerproduct of the reaction. Accordingly, this zone does not function as areaction zone.

In case of a continuously opening cone or gradually increasing innerdiameter, the shape of the third zone may be part of the shape of thesecond zone as illustrated by FIG. 9 herein. For example, thecontinuously opening cone or gradually increasing inner diameter mayextend from the second into the third zone and optionally also from thethird into the fourth zone.

However, the shape of the continuously opening cone or graduallyincreasing inner diameter of the third zone may also have a shape thatis different from the continuously opening cone or gradually increasinginner diameter of the second zone. The continuously opening cone orgradually increasing inner diameter of the third zone may be located inany part of the third zone, for example in the lower or in the upperpart of the third zone, but is preferably located in the lower part ofthe third zone.

The multi-zone reactor in this embodiment of the invention isschematically illustrated in FIG. 9 (FIG. 9).

The third zone may comprise part of the fluidized bed. The third zone issuitable for gas-phase polymerization.

The third zone and the second zone can be distinguished when themulti-zone reactor is operated; however there is no sharp boundarybetween the second and third zone. Typically, when operating themulti-zone reactor, the second zone will comprise more liquid than thethird zone and in the third zone, a gas-phase polymerization will takeplace.

The top zone of the of the multi-zone reactor, which is for example thefourth zone of the multi-zone reactor is located above the third zone.The top zone or fourth zone is not intended for gas-phasepolymerization, but instead is suitable for gas expansion. It has thefunction to disengage the reaction mixture and the polymer product ofthe reaction. Accordingly, this zone does not function as a reactionzone. The superficial gas velocity may be of such low value in that zonethat polymer particles preferably do not enter into the top zone,preferably at least so that the top recycle stream is sufficiently freeof particles to avoid clogging to occur in the compressor.

In such multi-zone reactor, during the course of polymerization, freshpolymer particles are produced by catalytic polymerization of α-olefinmonomers. Such polymer particles are projected upwards in the directionof the fourth zone through the circulating gas. Most of these particlesdo preferably not reach the fourth zone or return to the second or thirdzone by gravity as the superficial velocity decreases in the fourthzone. The fourth zone may be connected to the third zone or optionalfurther zone(s).

The multi-zone reactor (8) of the invention may comprise further zones,such as for example one, two or even optionally three further zones,that can for example be a fifth zone and optionally a sixth zone andoptionally even a seventh zone. These zones may provide a furtherpossibility for polymerization, wherein each further zone may beoperated at different reaction conditions. These further zones can belocated preferably between the third zone and the top zone.

With inner diameter is meant the diameter in a given horizontal planeperpendicular to the center line of the multi-zone reactor as measuredfrom the inside of the inner wall of the multi-zone reactor. The centerline (9) is illustrated in FIG. 9

For example, the maximum inner diameter of the fourth zone is at least1, for example at least 3, for example at least 5% and/or for example atmost 300%, for example at most 200%, for example at most 150%, forexample at most 80%, for example at most 70%, for example at most 60%,for example at most 50%, for example at most 40%, for example at most30%, for example at most 25%, for example at most 20%, for example atmost 15% larger than the maximum inner diameter of the third zone. Forexample, the maximum inner diameter of the fourth zone is from 5 to 30%larger than the maximum inner diameter of the third zone.

For example, the maximum inner diameter of the third zone is at least 1,for example at least 3, for example at least 5% and/or for example atmost 300%, for example at most 200%, for example at most 150%, forexample at most 80%, for example at most 70%, for example at most 60%,for example at most 50%, for example at most 40%, for example at most30%, for example at most 25%, for example at most 20%, for example atmost 15% larger than the maximum inner diameter of the second zone. Forexample, the maximum inner diameter of the third zone is from 15 to 30%larger than the maximum inner diameter of the second zone.

For example, the maximum inner diameter of the second zone is at least1, for example at least 3, for example at least 5% and/or for example atmost 300%, for example at most 200%, for example at most 150%, forexample at most 80%, for example at most 70%, for example at most 60%,for example at most 50%, for example at most 40%, for example at most30%, for example at most 25%, for example at most 20%, for example atmost 15% larger than the maximum inner diameter of the first zone. Forexample, the maximum inner diameter of the second zone is from 15 to 30%larger than the maximum inner diameter of the first zone.

In one embodiment, the invention relates to the reactor of theinvention, wherein at least the bottom part of the third zone comprisesan inner wall in the form of a gradually increasing inner diameter or acontinuously opening cone, wherein the diameter or the opening increasesin the vertical direction towards the top of the multi-zone reactor. Inthis embodiment, the bottom part of the second zone and/or of the bottompart of the fourth zone may also comprise an inner wall in the form of agradually increasing inner diameter or a continuously opening cone,wherein the diameter or the opening increases in the vertical directiontowards the top of the multi-zone reactor.

In one embodiment, as illustrated by FIG. 10 the zone (2) in the areadirectly above the distribution plate is either in the form of agradually increasing inner diameter or a continuously opening cone (2A),wherein the diameter or the opening increases in the vertical directiontowards the top of the multi-zone reactor and wherein the top part ofthe second zone has an inner wall having a cylindrical shape (2B) andwherein the top part of the second zone is connected to a bottom part ofthe third zone (3A), wherein the bottom part of the third zone is eitherin the form of a gradually increasing inner diameter or a continuouslyopening cone, wherein the diameter or the opening increases in thevertical direction towards the top of the multi-zone reactor and whereinthe top part of the third zone has an inner wall having a cylindricalshape (3B) and wherein the top part of the third zone is connected tothe top zone, for example to the fourth zone.

Therefore, preferably. zone (2) in the area directly above thedistribution plate is either in the form of a gradually increasing innerdiameter or a continuously opening cone (2A), wherein the diameter orthe opening increases in the vertical direction towards the top of themulti-zone reactor and wherein the top part of the second zone has aninner wall having a cylindrical shape (2B) and wherein the top part ofthe second zone is connected to a bottom part of the third zone (3A),wherein the bottom part of the third zone is either in the form of agradually increasing inner diameter or a continuously opening cone,wherein the diameter or the opening increases in the vertical directiontowards the top of the multi-zone reactor and wherein the top part ofthe third zone has an inner wall having a cylindrical shape (3B) andwherein the top part of the third zone is connected to the top zone, forexample to the fourth zone.

Preferably, the cylindrical shape is the shape of a right circularcylinder.

Preferably, the angle (α) of the inner wall of the part of the secondzone having the gradually increasing inner diameter or having thecontinuously opening cone, relative to the centre line (9) of themulti-zone reactor (8) is from 0.1 to 80 degrees, preferably from 1 to60 degrees, more preferably from 1-45 degrees, most preferably around 27degrees.

For example, said angle (α) is at least 5, for example at least 7, forexample at least 10 degrees, for example at least 20 degrees and/or forexample at most 60, for example at most 50, for example at most 40, forexample at most 35 degrees, for example at most 30 degrees. For example,the angle (α) is in the range from 10 to 40 degrees.

Preferably, the invention relates to a reactor of the invention, whereinthe angle (α) of the inner wall of the part of the third zone having thegradually increasing inner diameter or having the continuously openingcone, relative to the centre line (9) of the multi-zone reactor (8) isfrom 0.1 to 80 degrees, preferably from 1 to 60 degrees, more preferablyfrom 1-45 degrees, most preferably around 27 degrees, for example from 1to 40 degrees.

For example, said angle (α) is at least 5, for example at least 7, forexample at least 10 degrees, for example at least 20 degrees and/or forexample at most 60, for example at most 50, for example at most 40, forexample at most 35 degrees, for example at most 30 degrees. For example,the angle (α) is in the range from 10 to 40 degrees.

It should be appreciated by the skilled person that due to the fact thatthe volume in the multi-zone reactor of the invention expands from thefirst zone to the second zone and from the second zone to the third zoneand from the third zone to the fourth zone when operating the multi-zonereactor, the superficial gas velocities in these zones will decreasefrom the first to the second and from the second to the third zone andfrom the third zone to the fourth zone. For example, the superficial gasvelocities in the multi-zone reactor of the invention, for example whenused to produce polyethylene, for example LLDPE, may be in the range offrom 0.7 to 3.5 m/s, which may then be reduced to 0.5 to 2 m/s in thethird zone, after which the superficial gas velocity may be furtherreduced in the top zone.

In the invention, the slurry stream is preferably introduced into thepart of the second zone wherein the inner wall is either in the form ofa gradually increasing inner diameter or a continuously opening cone orinto the part of the third zone wherein the inner wall is either in theform of a gradually increasing inner diameter or a continuously openingcone.

Preferably. the bottom recycle stream is introduced in a direction thatis substantially tangential to the reactor wall.

Due to such tangential introduction, at least a part of the condensedliquid is separated by a ‘centrifugal effect’ involved in the area underthe distribution plate. Furthermore, depending on the type of integralseparator used, the centrifugal effect may cause additional condensationof the gas contained in the bottom recycle stream.

In one embodiment of the invention, the zone in the reactor above thedistribution plate (in case of the multi-zone reactor, the second zone)is divided into two or more subzones by one or more substantiallyvertical partition walls, for example a tube, extending from a pointlocated above the distribution plate to a point located below the gasexpansion zone (in case of the multi-zone reactor, the fourth zone)preferably such that a dead zone is prevented.

With ‘dead zone’ is meant a region where the mixing is insufficient forproviding homogeneous reaction resulting in either chunking or meltingin the dead zone and/or resin that is outside the desired specifications(off spec). Examples of specifications are not limited to desireddensity, molecular weight, molecular weight distribution and/or meltflow rate.

Such vertical partition walls are sometimes also referred to as ‘drafttube’. This is for example described in WO02/40146A1 and in U.S. Pat.No. 6,403,730, both of which are hereby incorporated by reference.

In one embodiment, the reactor further comprises a moving bed unit,wherein the moving bed unit is provided with an inlet and an outletwhich are connected to the zone in the reactor above the distributionplate (in case of the multi-zone reactor this is the second zone of thereactor), wherein in said zone shielding means are positioned such thatvia the outlet of the moving bed unit inflow of gas from said zone isinhibited and outflow of polymerization particles is allowed, whereinpreferably the moving bed unit is provided with gas feed means forfeeding gas at one or more different levels in the moving bed unitand/or wherein preferably the outlet of the moving bed unit is providedwith means for displacing metered quantities of polymer particles fromthe moving bed unit into the zone above the distribution plate.

US 20100273971, which is hereby incorporated by reference, disclosessuch moving bed unit (also known as ‘draught tube’), wherein the movingbed unit is provided with an inlet and an outlet which are connected tothe zone of the reactor above the distribution plate, wherein shieldingare positioned such that via the outlet of the moving bed unit inflow ofgas from the zone above the distribution plate is inhibited and outflowof polymerization particles is allowed.

Such draught tube is also described in U.S. Pat. No. 8,354,483, herebyincorporated by reference, which discloses that the moving bed unit isprovided with gas feed means for feeding gas at one or more differentlevels in the moving bed unit and preferably wherein the outlet of themoving bed unit is provided with means for displacing metered quantitiesof polymer particles from the moving bed unit into the zone above thedistribution plate. In order to maintain a fluidized bed in theprocesses of the invention, the superficial gas velocity is in the rangeof 0.5 to 5 m/s. For example, is at least 1, for example at least 1.5,for example at least 2 and/or for example at most 4.5, for example atmost 4, for example at most 3.5, for example at most 3 m/s.

By feeding the fluids that are cooled to below the dew point of thefluids into the first zone (1), the fluids will be passed from the firstzone (1) through the distribution plate (6) into the second zone (2),resulting in the formation of a fluidized bed and/or a bubble column.Heat generated by the polymerization will cause the liquids in thefluids to evaporate. The feeding of the solid polymerization catalystand the one or more α-olefin monomers to the multi-zone reactor (8) willresult in the formation of polyolefin (30), which is withdrawn from themulti-zone reactor (8). The top recycle stream is recirculated from thetop of the multi-zone reactor to the first zone (1). The one or moreα-olefin monomers and other fluids, such as hydrogen, an inert gas orliquid, for example a condensable inert component, may be added to thetop recycle stream to make up for reacted fluids before cooling thefluids to below the dew point of the fluids to form a bottom recyclestream.

The continuous polymerization of one or more α-olefin monomers willproduce polyolefins in the form of particles, herein also referred to as‘polyolefin’ (30). Examples of polyolefins which may thus produced,include a wide variety of polymers, for example polyethylene, forexample linear low density polyethylene (LLDPE), which may for examplebe prepared from ethylene and but-1-ene, 4-methylpent-1-ene orhex-1-ene, high density polyethylene (HDPE), which may for example beprepared from ethylene or from ethylene with a small portion of anα-olefin monomer having from 4 to 8 carbon atoms, for example but-1-ene,pent-1-ene, hex-1-ene or 4-methylpent-1-ene. Other examples include butare not limited to plastomers, elastomers, medium density polyethylene,polypropylene homopolymers and polypropylene copolymers, includingrandom copolymers, and block or multi-block copolymer and ethylenepropylene rubber (EPR).

Preferably, in the processes of the invention, the polyolefin producedis a polyethylene, for example linear low density polyethylene or highdensity polyethylene or a homopolypropylene or propylene-ethylene randomcopolymer.

Depending on their composition, the polyolefins obtained or obtainableby the process of the invention may have several advantages over thepolyolefins produced in a reactor different from the reactor of theinvention. For example, the impact of polypropylene impact copolymersmay be increased, the amount of carbon black in ethylene polymer rubbers(EPR) may be decreased, the molecular weight distribution ofpolyethylene may be broadened, the homogeneity of the polyolefin may beincreased, the residence time distribution may be narrower, theblockiness may be altered, the morphology may be changed, the bulkdensity may be changed etc.

Therefore, in another aspect, the invention relates to a polyolefinobtained or obtainable by the processes of the invention.

The figures as used herein are meant to illustrate the invention but isby no means meant to limit the invention thereto.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic illustration of an embodiment of the reactorsystem of the invention using a standard gas-phase reactor that issuitable for the continuous polymerization of one or more α-olefinmonomers.

FIG. 2 is a schematic illustration of a reactor system of the inventionusing a multizone reactor instead of the standard gas-phase reactor.

FIG. 3 is a schematic illustration of a reactor system of the inventionusing the standard gas-phase reactor, wherein a draft tube (100) ispresent inside the reactor.

FIG. 4 is a schematic illustration of a reactor system of the inventionusing a multizone reactor, wherein a draft tube (100) is present insidethe reactor.

FIG. 5 is a schematic illustration of a reactor system of the inventionusing the standard gas-phase reactor, wherein a draught tube (200) ispresent inside the reactor.

FIG. 6 is a schematic illustration of a reactor system of the inventionusing a multizone reactor, wherein a draught tube (200) is presentinside the reactor.

FIG. 7 is a schematic illustration of a reactor system of the inventionusing the standard gas-phase reactor, wherein the distribution plate (6)comprises a conical shape.

FIG. 8 is a schematic illustration of a reactor system of the inventionusing the multi-zone reactor, wherein the distribution plate (6)comprises a conical shape. schematically illustrates one embodiment ofthe vertical cross-section of the multi-zone reactor.

FIG. 10 schematically illustrates one embodiment of the verticalcross-section of the multi-zone reactor.

FIG. 11 schematically illustrates a particularly preferred embodiment ofthe system of the invention, using a multi-zone reactor.

In another aspect, the invention relates to a system suitable for thecontinuous polymerization of one or more α-olefin monomers of which atleast one is ethylene or propylene comprising a reactor (8), acompressor (400), a cooling unit (5) and an external pipe (11) for theproduction of a prepolymer and/or polymer,

wherein the reactor comprises a first outlet for a top recycle stream(40)

wherein the system comprises apparatus for condensing the top recyclestream into a bottom recycle stream

wherein the reactor comprises a first inlet for receiving a bottomrecycle stream (10),

wherein the first inlet for receiving the bottom recycle stream islocated underneath the distribution plate (6)

wherein the reactor comprises an integral separator (9) for separationof the bottom recycle stream into a gas/liquid and a liquid phase

wherein the integral separator (9) is located underneath thedistribution plate (6)

wherein the first inlet of the integral separator (9) is connected to afirst outlet for a liquid phase

wherein the first outlet for the liquid phase is connected to the secondoutlet of the reactor for the liquid phase

wherein the second outlet of the reactor provides the liquid phase tothe first inlet of the external pipe (11)

wherein the external pipe comprises a second inlet for receiving a solidpolymerization catalyst (20)

wherein the first outlet of the external pipe is connected to a secondinlet of the reactor for receiving a slurry phase comprising theprepolymer and/or polymer

wherein the reactor comprises a third outlet for providing polyolefin(30)

wherein the system comprises a first inlet for receiving a feed (60) andoptionally a second inlet for receiving a feed (70).

Preferably, the first inlet for receiving the bottom recycle stream ofthe reactor may extend in a direction that is substantially tangentialto the reactor wall. By having an inlet that is substantially tangentialto the reactor wall, the (at least part of the) condensed liquid will beseparated by the ‘centrifugal effect’ involved in the area under thedistribution plate (also referred to herein as the first zone in case amulti-zone reactor is present in the reaction system of the invention).

The second outlet of the reactor for the liquid phase in the reactionsystem of the invention is preferably located at the bottom part of thereactor, that is the first zone (1) in case a multi-zone reactor isused, more preferably at the lowest part of the reactor, that is thelowest part of the first zone (1)|case of the multi-zone reactor.

Preferably, the first inlet of the reactor for receiving a bottomrecycle stream (10) is situated not more than 1.5 m below thedistribution plate (6). Depending on the type of polymer produced andreaction conditions, such as for example the amount of liquid in thebottom recycle stream, the choice of components of the bottom recyclestream, the optional condensing agent, the temperature of the bottomrecycle stream (10) and the presence and concentration of carried overparticles in the bottom recycle stream (10), the dimensions of the zonebelow the distribution plate (in case of the multi-zone reactor thefirst zone (1)), and the reaction mixture, the optimal place for thefirst inlet of the reactor (8) may easily be determined by the personskilled in the art through routine experimentation.

A special embodiment of the system of the invention is schematicallyrepresented in FIG. 1 (FIG. 1) without however being limited thereto.The system of FIG. 3 is only one of numerous possible schematicarrangements. Thus, for example, the sequence of the equipment items inthe circulated gas line, particularly of the cooler and compressor canalso be reversed or further equipment items can be integrated into theline. Further elements such as systems for discharging the product andfor metering-in the catalyst are not shown in FIG. 1, such elements areknown to those skilled in the art and can be integrated into the reactorin a known manner.

The system of FIG. 1 is a reactor system that suitable for thecontinuous polymerization of one or more α-olefin monomers of which atleast one is ethylene or propylene comprising a reactor (8), acompressor (400), a cooling unit (5) and an external pipe (11) for theproduction of a prepolymer and/or polymer,

wherein the reactor comprises a first outlet for a top recycle stream(40),

wherein the system comprises apparatus for condensing the top recyclestream into a bottom recycle stream,

wherein the reactor comprises a first inlet for receiving a bottomrecycle stream (10),

wherein the first inlet for receiving the bottom recycle stream islocated underneath the distribution plate (6),

wherein the reactor comprises an integral separator (9) for separationof the bottom recycle stream into a gas/liquid and a liquid phase,

wherein the integral separator (9) is located underneath thedistribution plate (6),

wherein the first inlet of the integral separator (9) is connected to afirst outlet for a liquid phase,

wherein the first outlet for the liquid phase is connected to the secondoutlet of the reactor for the liquid phase,

wherein the second outlet of the reactor provides the liquid phase tothe first inlet of the external pipe (11),

wherein the external pipe comprises a second inlet for receiving a solidpolymerization catalyst (20),

wherein the first outlet of the external pipe is connected to a secondinlet of the reactor for receiving a slurry phase comprising theprepolymer and/or polymer,

wherein the reactor comprises a third outlet for providing polyolefin(30),

wherein the system comprises a first inlet for receiving a feed (60) andoptionally a second inlet for receiving a feed (70).

In the system of FIG. 1, the first outlet of the reactor is connected toa first inlet of a compressor (400) via a first connection means (AA),for instance pipes

wherein the compressor (400) comprises a first outlet for compressedfluids (50),

wherein the first outlet of the compressor (400) is connected to a firstinlet for compressed fluids of the cooling unit (5) via a secondconnection means (BB), wherein optionally the second connection means(BB), for instance pipes, comprises a first inlet for receiving the feed(70),wherein the cooling unit (5) comprises a first outlet for providing thebottom recycle stream (10) which first outlet of the cooling unit (5) isconnected to the first inlet of the reactor, wherein the firstconnection means (AA) comprises a first inlet for receiving a feed (60).

The system of the invention may further comprise a polymer withdrawalsystem, a polymer degassing system and a vent gas recovery system (notshown in the figures presented herein). The outlet for the recoveredcomponents (in liquid form) (80) from the vent gas recovery system maybe connected to the first inlet (70) of the second connection means(BB).

As described above, the optional additional solid polymerizationcatalyst (indicated with 20′ in the figures) may be fed at any positioninto the reactor, for example in the area above the distribution plateor at a combination of positions, but preferably, in case of themulti-zone reactor, it is fed to the second zone (2), preferably to thebottom part of the second zone (2A).

The feed (60) comprises a chain transfer agent, for example hydrogen andmay further comprise gaseous α-olefin monomers and insert gaseouscomponents, for example nitrogen.

The feed (70) comprises condensable inert components, for example acondensable inert component selected from the group of alkanes having 4to 20 carbon atoms, preferably 4 to 8 carbon atoms, and mixturesthereof, for example propane, n-butane, isobutene, n-pentane,isopentane, neopentane, n-hexane, isohexane or other saturatedhydrocarbons having 6 C-atoms, n-heptane, n-octane and other saturatedhydrocarbons having 7 or 8 C-atoms and any mixtures thereof; and mayfurther comprise condensable α-olefin monomers, α-olefin comonomersand/or mixtures thereof.

The condensable inert component is preferably selected from the group ofisopentane, n-hexane, n-butane, i-butane and mixtures thereof. Becauseof their more attractive pricing, preferably isopentane and/or n-hexaneare/is used as condensable inert component(s) in the feed (70).

When copolymers are produced, the process of the invention furthercomprises supplying a comonomer using feed (60) or (70) in case of anon-condensable comonomer and using feed (70) in case of a condensablecomonomer.

Preferably in the invention, the fluids are cooled to such extent thatthe amount of liquid in the bottom recycle stream (10) is at least 7% byweight, for example at least 9%, for example at least 14% by weightbased on the total amount of liquid and gas. For example, the amount ofliquid in the bottom recycle stream is at least 14.5%, for example atleast 20%, for example at least 25% and/or for example at most 95%, forexample at most 90%, for example at most 90%, for example at most 85%,for example at most 80%, for example at most 75%, for example at most70%, for example at most 65%, for example at most 60%, for example atmost 55%, for example at most 55% by weight based on the total amount ofliquid and gas in the bottom recycle stream. Preferably, the amount ofliquid in the bottom recycle stream is at least 25% and for example atmost 55% by weight based on the total amount of liquid and gas in saidbottom recycle stream.

High amounts of liquid in the bottom recycle stream enables feeding ofone or more very high activity catalyst system.

In a preferred embodiment, the invention relates to a system of theinvention wherein the first outlet of the reactor is connected to afirst inlet of a compressor (400) via a first connection means (AA), forinstance pipes

wherein the compressor (400) comprises a first outlet for compressedfluids (50),

wherein the first outlet of the compressor (400) is connected to a firstinlet for compressed fluids of the cooling unit (5) via a secondconnection means (BB), wherein optionally the second connection means(BB), for instance pipes, comprises a first inlet for receiving the feed(70),wherein the cooling unit (5) comprises a first outlet for providing thebottom recycle stream (10) which first outlet of the cooling unit (5) isconnected to the first inlet of the reactor, wherein the firstconnection means (AA) comprises a first inlet for receiving a feed (60).

The compressor (400) may be any device that is suitable for compressingthe feed (60) and the top recycle stream (40) using the compressor (400)to form the compressed fluids (50). By compressing the feed (60) and thetop recycle stream (40), the pressure of the compressed fluids (50) isincreased compared to the feed (60) and the top recycle stream (40)before use of the compressor (400).

The cooling unit (5) may be any device that is suitable for cooling thecompressed fluids (50) to below the dew point of the compressed fluidsto form the bottom recycle stream (10). For example, a heat exchangermay be used as the cooling unit (5).

The top recycle stream (40) contains fluids that are withdrawn from thefirst outlet of the fourth zone (4) or in case of more than four zones,from the first outlet of the top zone of the (multi-zone) reactor (8).

The first connection means (AA) and the second connection means (BB) canin principle be any means for connecting the first outlet of the fourthzone (4) and the first inlet of the compressor (400) respectively, thefirst outlet of the compressor (400) and the first inlet of the coolingunit (5).

Preferably, in the system of the invention the external pipe (11) is aloop reactor as described herein.

For example, in the system of the invention, the distribution plate (6)(as described above) comprises a conical shape.

FIG. 7 (FIG. 7) is a schematic representation of a reactor system of theinvention using the standard gas-phase reactor, wherein the distributionplate (6) comprises a conical shape. FIG. 8 (FIG. 8) is a schematicrepresentation of a reactor system of the invention using the multi-zonereactor, wherein the distribution plate (6) comprises a conical shape.

In FIG. 7 and in FIG. 8, the apex of the cone points towards the top ofthe reactor.

In one embodiment of the system of the invention, the zone in thereactor above the distribution plate is divided into two or moresubzones by one or more substantially vertical partition walls, forexample a tube, extending from a point located above the distributionplate to a point located below the end surface such that a dead zone isprevented. This division into two or more subzones is also referred toherein as ‘draft tube’.

The system of FIG. 3 (FIG. 3) is a schematic representation of a reactorsystem of the invention using the standard gas-phase, wherein a drafttube is present inside the reactor. The system of FIG. 4 (FIG. 4) uses amultizone reactor instead of the standard gas-phase olefinpolymerization reactor as indicated in FIG. 3.

In one embodiment of the system of the invention, the reactor furthercomprises a moving bed unit, wherein the moving bed unit is providedwith an inlet and an outlet which are connected to the zone in thereactor above the distribution plate, wherein in said zone shieldingmeans are positioned such that via the outlet of the moving bed unitinflow of gas from said zone is inhibited and outflow of polymerizationparticles is allowed, wherein preferably the moving bed unit is providedwith gas feed means for feeding gas at one or more different levels inthe moving bed unit and/or wherein preferably the outlet of the movingbed unit is provided with means for displacing metered quantities ofpolymer particles from the moving bed unit into the zone above thedistribution plate. This moving bed unit is herein also referred to as‘draught tube’.

FIG. 5 (FIG. 5) is a schematic representation of a reactor system of theinvention using the standard gas-phase reactor, wherein a draught tubeis present inside the reactor. The system of FIG. 6 (FIG. 6) uses amultizone reactor instead of the standard gas-phase olefinpolymerization reactor as indicated in FIG. 5.

In a special embodiment of the system of the invention, the reactor (8)is a multi-zone reactor suitable for the continuous fluidized bedpolymerization of one or more α-olefin monomers of which at least one isethylene or propylene, which multi-zone reactor is operable in condensedmode, which multi-zone reactor is as described herein, i.e. whichmulti-zone reactor comprises a first zone, a second zone, a third zone,a fourth zone and a distribution plate,

wherein the first zone is separated from the second zone by thedistribution plate,

wherein the multi-zone reactor is extended in the vertical direction

wherein the second zone of the multi-zone reactor is located above thefirst zone and

wherein the third zone of the multi-zone reactor is located above thesecond zone,

and wherein the fourth zone of the multi-zone reactor is located abovethe third zone

wherein the second zone contains an inner wall, wherein at least part ofthe inner wall of the second zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactorwherein the third zone contains an inner wall, wherein at least part ofthe inner wall of the third zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactorwherein the largest diameter of the inner wall of the third zone islarger than the largest diameter of the inner wall of the second zone.

The system of FIG. 2 (FIG. 2) is a schematic representation of a reactorsystem of the invention. Instead of the standard gas-phase olefinpolymerization reactor as indicated in FIG. 1, a multizone reactor isused.

Preferably, the second inlet of the reactor for receiving a slurry phasecomprising the prepolymer and/or polymer is located in the part of thesecond zone wherein the inner wall is either in the form of a graduallyincreasing inner diameter or a continuously opening cone and/or in thepart of the third zone wherein the inner wall is either in the form of agradually increasing inner diameter or a continuously opening cone,preferably wherein the second inlet of the reactor for receiving aslurry phase comprising the prepolymer and/or polymer is located in thepart of the second zone wherein the inner wall is either in the form ofa gradually increasing inner diameter or a continuously opening cone.

Preferably, in the multi-zone reactor in zone (2) the area directlyabove the distribution plate is either in the form of a graduallyincreasing inner diameter or a continuously opening cone (2A), whereinthe diameter or the opening increases in the vertical direction towardsthe top of the multi-zone reactor and wherein the top part of the secondzone has an inner wall having a cylindrical shape (2B) and wherein thetop part of the second zone is connected to a bottom part of the thirdzone (3A), wherein the bottom part of the third zone is either in theform of a gradually increasing inner diameter or a continuously openingcone, wherein the diameter or the opening increases in the verticaldirection towards the top of the multi-zone reactor and wherein the toppart of the third zone has an inner wall having a cylindrical shape (3B)and wherein the top part of the third zone is connected to the top zone,for example to the fourth zone.

Preferably the third outlet of the reactor (30) below the third inletfor receiving the slurry phase comprising the prepolymer and/or polymeris located below the third inlet for receiving the slurry phase.

In case of the multi-zone reactor, preferably, the third outlet of thereactor (30) is located in the second or third zone, more preferablybelow the third inlet for receiving the slurry phase.

Preferably, the first inlet of the reactor for receiving the bottomrecycle stream is substantially tangential to the reactor wall.

The system of FIG. 11 is a reactor system that suitable for thecontinuous polymerization of one or more α-olefin monomers of which atleast one is ethylene or propylene comprising a reactor (8), acompressor (400), a cooling unit (5) and an external pipe (11) for theproduction of a prepolymer and/or polymer,

wherein the reactor comprises a first outlet for a top recycle stream(40),

wherein the system comprises apparatus for condensing the top recyclestream into a bottom recycle stream,

wherein the reactor comprises a first inlet for receiving a bottomrecycle stream (10),

wherein the first inlet for receiving the bottom recycle stream islocated underneath the distribution plate (6),

wherein the reactor comprises an integral separator (9) for separationof the bottom recycle stream into a gas/liquid and a liquid phase,

wherein the integral separator (9) is located underneath thedistribution plate (6),

wherein the first inlet of the integral separator (9) is connected to afirst outlet for a liquid phase,

wherein the first outlet for the liquid phase is connected to the secondoutlet of the reactor for the liquid phase,

wherein the second outlet of the reactor provides the liquid phase tothe first inlet of the external pipe (11),

wherein the external pipe comprises a second inlet for receiving a solidpolymerization catalyst (20),

wherein the first outlet of the external pipe is connected to a secondinlet of the reactor for receiving a slurry phase comprising theprepolymer and/or polymer,

wherein the reactor comprises a third outlet for providing polyolefin(30),

wherein the system comprises a first inlet for receiving a feed (60) andoptionally a second inlet for receiving a feed (70).

wherein the first outlet of the reactor is connected to a first inlet ofa compressor (400) via a first connection means (AA), for instance pipes

wherein the compressor (400) comprises a first outlet for compressedfluids (50),

wherein the first outlet of the compressor (400) is connected to a firstinlet for compressed fluids of the cooling unit (5) via a secondconnection means (BB), wherein optionally the second connection means(BB), for instance pipes, comprises a first inlet for receiving the feed(70),wherein the cooling unit (5) comprises a first outlet for providing thebottom recycle stream (10) which first outlet of the cooling unit (5) isconnected to the first inlet of the reactor, wherein the firstconnection means (AA) comprises a first inlet for receiving a feed (60)wherein the reactor is a multi-zone reactor suitable for the continuousfluidized bed polymerization of one or more α-olefin monomers of whichat least one is ethylene or propylene, which multi-zone reactor isoperable in condensed mode, which multi-zone reactor comprises a firstzone, a second zone, a third zone, a fourth zone and a distributionplate,wherein the first zone is separated from the second zone by thedistribution plate,wherein the multi-zone reactor is extended in the vertical direction,wherein the second zone of the multi-zone reactor is located above thefirst zone andwherein the third zone of the multi-zone reactor is located above thesecond zone,and wherein the fourth zone of the multi-zone reactor is located abovethe third zone,wherein the second zone contains an inner wall, wherein at least part ofthe inner wall of the second zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactor,wherein the third zone contains an inner wall, wherein at least part ofthe inner wall of the third zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone, wherein thediameter or the opening increases in the vertical direction towards thetop of the multi-zone reactor,wherein the largest diameter of the inner wall of the third zone islarger than the largest diameter of the inner wall of the second zone,wherein zone (2) in the area directly above the distribution plate iseither in the form of a gradually increasing inner diameter or acontinuously opening cone (2A), wherein the diameter or the openingincreases in the vertical direction towards the top of the multi-zonereactor and wherein the top part of the second zone has an inner wallhaving a cylindrical shape (2B) and wherein the top part of the secondzone is connected to a bottom part of the third zone (3A), wherein thebottom part of the third zone is either in the form of a graduallyincreasing inner diameter or a continuously opening cone,wherein the diameter or the opening increases in the vertical directiontowards the top of the multi-zone reactor and wherein the top part ofthe third zone has an inner wall having a cylindrical shape (3B) andwherein the top part of the third zone is connected to the top zone, forexample to the fourth zone,wherein the third outlet of the reactor (30) is located in the second orthird zone, more preferably below the third inlet for receiving theslurry phase,wherein the feed for the optional additional solid polymerizationcatalyst (20′) is located at the bottom part of the second zone (2A) andwherein the second inlet of the reactor for receiving a slurry phasecomprising the prepolymer and/or polymer is located in the part of thesecond zone wherein the inner wall is either in the form of a graduallyincreasing inner diameter or a continuously opening cone and/or in thepart of the third zone wherein the inner wall is either in the form of agradually increasing inner diameter or a continuously opening cone,preferably wherein the second inlet of the reactor for receiving aslurry phase comprising the prepolymer and/or polymer is located in thepart of the second zone wherein the inner wall is either in the form ofa gradually increasing inner diameter or a continuously opening cone.

In another aspect, the invention relates to a process for the continuouspolymerization of one or more α-olefin monomers of which at least one isethylene or propylene to produce a polyolefin in the system of theinvention.

In the reaction system and processes of the invention, hydrogen may forinstance be used as a chain transfer agent to adjust the molecularweight of the polyolefin (30) produced.

The processes of the invention are preferably conducted in anenvironment that is substantially free of water, oxygen and carbondioxide, since the presence of water may negatively influence theactivity of the solid polymerization catalyst.

Depending on which polyolefin is to be produced, the optimal reactionconditions can easily be determined by the person skilled in the art.

For example, generally, the temperature in the second zone (2) ispreferably in the range from 0 to 130° C., for example from 20 to 110°C.

For example, generally, the temperature in the third zone (3) ispreferably in the range from 20 to 130° C.

For example, the pressure in the multi-zone reactor (8) is preferably inthe range from 0.1 to 10 MPa, for example in the range of 0.2 to 8 MPa.

More, in particular, the invention relates to a process for thecontinuous polymerization of one or more α-olefin monomers of which atleast one is ethylene or propylene to produce a polyolefin in the systemof the invention comprising the steps of

-   -   supplying the external pipe (11) with a solid polymerization        catalyst using the second inlet for receiving the solid        polymerization catalyst to form a slurry comprising prepolymer        and/or polymer, wherein the prepolymer and/or polymer are        present in the slurry stream in an amount of from 0.01 to 99 wt        % based on the total slurry stream upon introduction of the        slurry stream into the reactor.    -   feeding the slurry stream comprising the prepolymer and/or        polymer into the second inlet of the reactor above the        distribution plate    -   supplying a feed (60) comprising an α-olefin monomer and        optionally supplying a feed (70) comprising condensable inert        components into the apparatus for condensing the top recycle        stream into a bottom recycle stream    -   withdrawing the polyolefin (30) using the third outlet of the        reactor    -   circulating fluids from the first outlet of the reactor to the        first inlet of the reactor        wherein the fluids are circulated by    -   compressing the feed (60) and the top recycle stream (40) using        the apparatus for condensing the top recycle stream into a        bottom recycle stream to below the dew point of the compressed        fluids to form the bottom recycle stream (10) and    -   feeding the bottom recycle stream (10) to the first zone of the        multi-zone reactor (8) via the first inlet for receiving the        bottom recycle stream and into the first inlet of the integral        separator (9).

Even more in particular, the invention relates to a process according tothe invention, for the continuous polymerization of one or more α-olefinmonomers of which at least one is ethylene or propylene to produce apolyolefin in the system of the invention,

wherein a feed (60) is supplied to the first connection means (AA) andwherein optionally feed (70) is supplied to the second connection means(BB) and|

wherein the top recycle stream is condensed into the bottom recyclestream by compressing the feed (60) and the top recycle stream (40)using the compressor (400) to form compressed fluids (50) and whereinthe compressed fluids (50) are cooled to below the dew point of thecompressed fluids using the cooling unit (5) to form the bottom recyclestream (10).

As described above, the polyolefins produced using the processes of theinvention have several advantages. Therefore, in another aspect, theinvention relates to a polyolefin, preferably a homopolypropylene orpropylene ethylene random copolymer or linear low density polyethyleneor high density polyethylene obtained or obtainable by the process ofthe invention.

In another aspect, the invention relates to the use of the system of theinvention for continuous polymerization of one or more α-olefin monomersof which at least one is ethylene or propylene.

It is further noted that the term ‘comprising’ does not exclude thepresence of other elements. However, it is also to be understood that adescription on a product comprising certain components also discloses aproduct consisting of these components. Similarly, it is also to beunderstood that a description on a process comprising certain steps alsodiscloses a process consisting of these steps.

The invention claimed is:
 1. A process for the continuous polymerization of one or more α-olefin monomers of which at least one is ethylene or propylene comprising: (1) feeding the one or more α-olefins to a vertically extended reactor suitable for the continuous fluidized bed polymerization of one or more α-olefin monomers of which at least one is ethylene or propylene, which reactor is operable in condensed mode, wherein the reactor comprises a distribution plate and an integral gas/liquid separator located below the distribution plate, (2) withdrawing the polyolefin from the reactor, (3) withdrawing fluids from the top of the reactor, (4) cooling the fluids to below their dew point, resulting in a bottom recycle stream, (5) introducing the bottom recycle stream under the distribution plate, (6) separating at least part of the liquid from the bottom recycle stream using the integral separator to form a liquid phase and a gas/liquid phase, wherein the liquid comprises prepolymer, (7) feeding the liquid phase to an external pipe, (8) adding a solid polymerization catalyst to the liquid phase in the external pipe resulting in the formation of a slurry stream comprising prepolymer and/or polymer, and (9) feeding the slurry stream comprising the prepolymer and/or polymer into the reactor above the distribution plate, wherein the prepolymer and/or polymer are present in the slurry stream in an amount of from 0.01 to 99 wt % based on the total slurry stream upon introduction of the slurry stream into the reactor.
 2. The process according to claim 1, wherein the external pipe is a loop reactor.
 3. The process according to claim 1, wherein the reactor is a multi-zone reactor suitable for the continuous fluidized bed polymerization of one or more α-olefin monomers of which at least one is ethylene or propylene, which multi-zone reactor is operable in condensed mode, which multi-zone reactor comprises a first zone, a second zone, a third zone, a fourth zone and a distribution plate, wherein the first zone is separated from the second zone by the distribution plate, wherein the multi-zone reactor is extended in the vertical direction, wherein the second zone of the multi-zone reactor is located above the first zone, and wherein the third zone of the multi-zone reactor is located above the second zone, and wherein the fourth zone of the multi-zone reactor is located above the third zone, wherein the second zone contains an inner wall, wherein at least part of the inner wall of the second zone is either in the form of a gradually increasing inner diameter or a continuously opening cone, wherein the diameter or the opening increases in the vertical direction towards the top of the multi-zone reactor, wherein the third zone contains an inner wall, wherein at least part of the inner wall of the third zone is either in the form of a gradually increasing inner diameter or a continuously opening cone, wherein the diameter or the opening increases in the vertical direction towards the top of the multi-zone reactor, wherein the largest diameter of the inner wall of the third zone is larger than the largest diameter of the inner wall of the second zone.
 4. The process according to claim 3, wherein zone in the area directly above the distribution plate is either in the form of a gradually increasing inner diameter or a continuously opening cone, wherein the diameter or the opening increases in the vertical direction towards the top of the multi-zone reactor and wherein the top part of the second zone has an inner wall having a cylindrical shape and wherein the top part of the second zone is connected to a bottom part of the third zone, wherein the bottom part of the third zone is either in the form of a gradually increasing inner diameter or a continuously opening cone, wherein the diameter or the opening increases in the vertical direction towards the top of the multi-zone reactor and wherein the top part of the third zone has an inner wall having a cylindrical shape and wherein the top part of the third zone is connected to the top zone.
 5. The process according to claim 3, wherein the angle of the inner wall of the part of the second zone having the gradually increasing inner diameter or having the continuously opening cone, relative to the center line of the multi-zone reactor is from 0.1 to 80 degrees.
 6. The process according to claim 3, wherein the slurry stream is introduced into the part of the second zone wherein the inner wall is either in the form of a gradually increasing inner diameter or a continuously opening cone or into the part of the third zone wherein the inner wall is either in the form of a gradually increasing inner diameter or a continuously opening cone.
 7. The process according to claim 3, wherein the bottom recycle stream is introduced in a direction that is substantially tangential to the reactor wall.
 8. The process according to claim 1, wherein the integral separator is a hydrocyclone, cyclone or a wet scrubber, each of which may optionally be combined with a flow deflector and/or spinner.
 9. The process according to claim 1, wherein the distribution plate comprises a conical shape.
 10. The process according to claim 1, wherein the zone in the reactor above the distribution plate is divided into two or more subzones by one or more substantially vertical partition walls, extending from a point located above the distribution plate to a point located below the gas expansion zone.
 11. The process according to claim 1, wherein the reactor further comprises a moving bed unit, wherein the moving bed unit is provided with an inlet and an outlet which are connected to the zone in the reactor above the distribution plate, wherein in said zone shielding means are positioned such that via the outlet of the moving bed unit inflow of gas from said zone is inhibited and outflow of polymerization particles is allowed.
 12. The process according to claim 4, wherein the top part of the third zone is connected to the fourth zone.
 13. The process according to claim 8, wherein the integral separator is a hydrocyclone.
 14. The process according to claim 10, wherein the zone in the reactor above the distribution plate is divided into two or more subzones by a tube.
 15. The process according to claim 11, wherein the moving bed unit is provided with gas feed means for feeding gas at one or more different levels in the moving bed unit and/or wherein the outlet of the moving bed unit is provided with means for displacing metered quantities of polymer particles from the moving bed unit into the zone above the distribution plate. 